R:igraph中的K最短路径
我必须找到K条最短路径，但是当我选择不同的R:igraph中的K最短路径,r,igraph,shortest-path,R,Igraph,Shortest Path,我必须找到K条最短路径，但是当我选择不同的K值时，下面的代码给出了相同的路径，并且计算的距离不正确 我的数据集是My.graph和classigraph dput(my.graph) structure(list(169, FALSE, c(22, 1, 2, 1, 2, 3, 114, 3, 4, 5, 4, 5, 6, 6, 7, 7, 8, 9, 8, 110, 78, 159, 9, 159, 30, 11, 13, 160, 11, 66, 160, 138
KMy.graphigraphdput(my.graph)
structure(list(169, FALSE, c(22, 1, 2, 1, 2, 3, 114, 3, 4, 5,
4, 5, 6, 6, 7, 7, 8, 9, 8, 110, 78, 159, 9, 159, 30, 11, 13,
160, 11, 66, 160, 138, 14, 13, 14, 15, 81, 16, 15, 17, 16, 17,
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372), list(c(1, 0, 1), structure(list(), .Names = character(0)),
structure(list(name = c("1", "2", "3", "4", "5", "6", "7",
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)), .Names = "name"), structure(list(DIST_KM_CNT = c(4.89,
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0.905, 1.317, 0, 1.317)), .Names = "DIST_KM_CNT")), <environment>), class = "igraph")
我也有同样的问题，然后我注意到代码中有一个错误。函数contains.path中相同的函数未返回正确的值。我只是将相同（x$variant$vert，variant）的代码更改为相同（unlist（x$variant$vert），unlist（variant））。现在代码报告了所有路线，没有重复的路线出现。我知道这已经晚了两年，但希望这对其他需要在R中实现yen算法的人有用
library(igraph)
library(tidyverse)
#'@return the shortest path as a list of vertices or NULL if there is no path between src and dest
shortest_path <- function(graph, src, dest){
path <- suppressWarnings(get.shortest.paths(graph, src, dest))
path <- names(path$vpath[[1]])
if (length(path)==1) NULL else path
}
#'@return the sum of the weights of all the edges in the given path
path_weight <- function(path, graph) sum(E(graph, path=path)$weight)
#'@description sorts a list of paths based on the weight of the path
sort_paths <- function(graph, paths) paths[paths %>% sapply(path_weight, graph) %>% order]
#'@description creates a list of edges that should be deleted
find_edges_to_delete <- function(A,i,rootPath){
edgesToDelete <- NULL
for (p in A){
rootPath_p <- p[1:i]
if (all(rootPath_p == rootPath)){
edge <- paste(p[i], ifelse(is.na(p[i+1]),p[i],p[i+1]), sep = '|')
edgesToDelete[length(edgesToDelete)+1] <- edge
}
}
unique(edgesToDelete)
}
#returns the k shortest path from src to dest
#sometimes it will return less than k shortest paths. This occurs when the max possible number of paths are less than k
k_shortest_yen <- function(graph, src, dest, k){
if (src == dest) stop('src and dest can not be the same (currently)')
#accepted paths
A <- list(shortest_path(graph, src, dest))
if (k == 1) return (A)
#potential paths
B <- list()
for (k_i in 2:k){
prev_path <- A[[k_i-1]]
num_nodes_to_loop <- length(prev_path)-1
for(i in 1:num_nodes_to_loop){
spurNode <- prev_path[i]
rootPath <- prev_path[1:i]
edgesToDelete <- find_edges_to_delete(A, i,rootPath)
t_g <- delete.edges(graph, edgesToDelete)
#for (edge in edgesToDelete) t_g <- delete.edges(t_g, edge)
spurPath <- shortest_path(t_g,spurNode, dest)
if (!is.null(spurPath)){
total_path <- list(c(rootPath[-i], spurPath))
if (!total_path %in% B) B[length(B)+1] <- total_path
}
}
if (length(B) == 0) break
B <- sort_paths(graph, B)
A[k_i] <- B[1]
B <- B[-1]
}
A
}
#===================Test==========================#
edgeList <- tibble(from=character(), to=character(), weight = numeric())
edgeList[nrow(edgeList)+1,] <-list('c','d',3)
edgeList[nrow(edgeList)+1,] <-list('d','f',4)
edgeList[nrow(edgeList)+1,] <-list('f','h',1)
edgeList[nrow(edgeList)+1,] <-list('c','e',2)
edgeList[nrow(edgeList)+1,] <-list('e','d',1)
edgeList[nrow(edgeList)+1,] <-list('e','f',2)
edgeList[nrow(edgeList)+1,] <-list('e','g',3)
edgeList[nrow(edgeList)+1,] <-list('g','h',2)
edgeList[nrow(edgeList)+1,] <-list('f','g',2)
graph <- graph.data.frame(edgeList)
#k_shortest.yen(graph, 'c','c',7) #expect error
#expect all 7 paths
k_shortest_yen(graph,'c','h',7)
库（igraph）
图书馆（tidyverse）
#“@将最短路径作为顶点列表返回，如果src和dest之间没有路径，则返回NULL
“最短路径”如果您发布一篇关于您试图执行的操作的文章，而不是使用整个数据集，您将有更好的机会获得答案。@Bryan数据集有342行3列。这是简化的数据集这可能是简化的数据集，但最好使用最小的数据集。问题的最简单版本是什么，它仍然抓住了您试图解决的问题的相关元素？此外，您可以提供更简单的上下文，而不是仅使用dput
转储igraph
对象，例如，从几个边和节点开始创建igraph
对象。这将帮助其他人从你试图做的事情中学习，并使答案更加笼统。最后，说出你所说的“不正确”是什么意思。你怎么知道它是不正确的？你期望什么？我怎么能看到链接权重的总和？？！结果仅显示[[1]]$g、[[1]]$path、[[1]]$vert和[[1]]$dist。[[1]]$dist仅显示节点数。我想把这个值乘以重量！！谢谢，我怎样才能看到链接权重的总和？？！结果仅显示[[1]]$g、[[1]]$path、[[1]]$vert和[[1]]$dist。[[1]]$dist仅显示节点数。我想把这个值乘以重量！！谢谢，这对我很有帮助。但是，是否可以计算路径的权重值？？！我指的是路径旅行时间。结果仅显示遍历节点。谢谢
library(igraph)
k.shortest.paths(my.graph, from = 37, to = 8, k = 2)
[[1]]
[[1]]$g
IGRAPH UN-- 169 372 --
+ attr: name (v/c), DIST_KM_CNT (e/n)
+ edges (vertex names):
[1] 1 --23 1 --2 2 --3 1 --2 2 --3 3 --4 3 --115 3 --4 4 --5
[10] 5 --6 4 --5 5 --6 6 --7 6 --7 7 --8 7 --8 8 --9 9 --10
[19] 8 --9 10--111 10--79 10--160 9 --10 11--160 11--31 11--12 12--14
[28] 12--161 11--12 13--67 13--161 13--139 14--15 12--14 14--15 15--16
[37] 15--82 16--17 15--16 17--18 16--17 17--18 18--19 18--19 19--20
[46] 20--131 19--20 20--63 21--63 21--24 22--43 22--23 1 --23 22--23
[55] 21--24 24--25 24--162 24--25 25--26 25--26 26--27 27--65 26--27
[64] 28--29 28--162 29--30 28--29 29--30 30--48 30--49 30--54 31--143
+ ... omitted several edges
[[1]]$path
[[1]]$path[[1]]
+ 11/372 edges (vertex names):
[1] 36--37 35--36 34--35 33--34 32--33 31--32 11--31 11--160 10--160
[10] 9 --10 8 --9
[[1]]$vert
[[1]]$vert[[1]]
+ 12/169 vertices, named:
[1] 37 36 35 34 33 32 31 11 160 10 9 8
[[1]]$dist
8
37 11
[[2]]
[[2]]$g
IGRAPH UN-- 169 371 --
+ attr: name (v/c), DIST_KM_CNT (e/n)
+ edges (vertex names):
[1] 1 --23 1 --2 2 --3 1 --2 2 --3 3 --4 3 --115 3 --4 4 --5
[10] 5 --6 4 --5 5 --6 6 --7 6 --7 7 --8 7 --8 8 --9 9 --10
[19] 8 --9 10--111 10--79 10--160 9 --10 11--160 11--31 11--12 12--14
[28] 12--161 11--12 13--67 13--161 13--139 14--15 12--14 14--15 15--16
[37] 15--82 16--17 15--16 17--18 16--17 17--18 18--19 18--19 19--20
[46] 20--131 19--20 20--63 21--63 21--24 22--43 22--23 1 --23 22--23
[55] 21--24 24--25 24--162 24--25 25--26 25--26 26--27 27--65 26--27
[64] 28--29 28--162 29--30 28--29 29--30 30--48 30--49 30--54 31--143
+ ... omitted several edges
[[2]]$path
[[2]]$path[[1]]
+ 11/371 edges (vertex names):
[1] 36--37 35--36 34--35 33--34 32--33 31--32 11--31 11--160 10--160
[10] 9 --10 8 --9
[[2]]$vert
[[2]]$vert[[1]]
+ 12/169 vertices, named:
[1] 37 36 35 34 33 32 31 11 160 10 9 8
[[2]]$dist
8
37 11
library(igraph)
library(tidyverse)
#'@return the shortest path as a list of vertices or NULL if there is no path between src and dest
shortest_path <- function(graph, src, dest){
path <- suppressWarnings(get.shortest.paths(graph, src, dest))
path <- names(path$vpath[[1]])
if (length(path)==1) NULL else path
}
#'@return the sum of the weights of all the edges in the given path
path_weight <- function(path, graph) sum(E(graph, path=path)$weight)
#'@description sorts a list of paths based on the weight of the path
sort_paths <- function(graph, paths) paths[paths %>% sapply(path_weight, graph) %>% order]
#'@description creates a list of edges that should be deleted
find_edges_to_delete <- function(A,i,rootPath){
edgesToDelete <- NULL
for (p in A){
rootPath_p <- p[1:i]
if (all(rootPath_p == rootPath)){
edge <- paste(p[i], ifelse(is.na(p[i+1]),p[i],p[i+1]), sep = '|')
edgesToDelete[length(edgesToDelete)+1] <- edge
}
}
unique(edgesToDelete)
}
#returns the k shortest path from src to dest
#sometimes it will return less than k shortest paths. This occurs when the max possible number of paths are less than k
k_shortest_yen <- function(graph, src, dest, k){
if (src == dest) stop('src and dest can not be the same (currently)')
#accepted paths
A <- list(shortest_path(graph, src, dest))
if (k == 1) return (A)
#potential paths
B <- list()
for (k_i in 2:k){
prev_path <- A[[k_i-1]]
num_nodes_to_loop <- length(prev_path)-1
for(i in 1:num_nodes_to_loop){
spurNode <- prev_path[i]
rootPath <- prev_path[1:i]
edgesToDelete <- find_edges_to_delete(A, i,rootPath)
t_g <- delete.edges(graph, edgesToDelete)
#for (edge in edgesToDelete) t_g <- delete.edges(t_g, edge)
spurPath <- shortest_path(t_g,spurNode, dest)
if (!is.null(spurPath)){
total_path <- list(c(rootPath[-i], spurPath))
if (!total_path %in% B) B[length(B)+1] <- total_path
}
}
if (length(B) == 0) break
B <- sort_paths(graph, B)
A[k_i] <- B[1]
B <- B[-1]
}
A
}
#===================Test==========================#
edgeList <- tibble(from=character(), to=character(), weight = numeric())
edgeList[nrow(edgeList)+1,] <-list('c','d',3)
edgeList[nrow(edgeList)+1,] <-list('d','f',4)
edgeList[nrow(edgeList)+1,] <-list('f','h',1)
edgeList[nrow(edgeList)+1,] <-list('c','e',2)
edgeList[nrow(edgeList)+1,] <-list('e','d',1)
edgeList[nrow(edgeList)+1,] <-list('e','f',2)
edgeList[nrow(edgeList)+1,] <-list('e','g',3)
edgeList[nrow(edgeList)+1,] <-list('g','h',2)
edgeList[nrow(edgeList)+1,] <-list('f','g',2)
graph <- graph.data.frame(edgeList)
#k_shortest.yen(graph, 'c','c',7) #expect error
#expect all 7 paths
k_shortest_yen(graph,'c','h',7)